O'Rourke is aware that the incumbent Senator Ted Cruz has tried to use the El Paso congressman's stance on impeaching Trump as a way to turn more conservative voters against the Democrat in the midterms. But O'Rourke hasn't changed his mind.

CNN's Dana Bash prompted the dialogue, asking O'Rourke if he'd reconsidered. The Senate candidate said his support for impeaching Trump comes from the ongoing probe of whether the president colluded with Russia during his 2016 campaign.

"When we saw him on that stage in Helsinki defending Vladimir Putin, the head of the country that attacked our democracy in 2016, instead of this country, and its citizens and this amazing democracy, that was collusion in action," O'Rourke said Thursday night in McAllen.

He also pointed out the firing of James Comey, who was the principal investigator into the ties between Trump and Russia. For O'Rourke, he said Trump calling for Attorney General Jeff Sessions to end the Russia investigation via Twitter was "obstruction in action."

..This is a terrible situation and Attorney General Jeff Sessions should stop this Rigged Witch Hunt right now, before it continues to stain our country any further. Bob Mueller is totally conflicted, and his 17 Angry Democrats that are doing his dirty work are a disgrace to USA!

"There is enough there to proceed to a trial," O'Rourke said. Though he said he wouldn't "prejudge the outcome," he does believe there's enough evidence for Trump to be held accountable and judged in court.

O'Rourke's national town hall comes days before Trump is expected to campaign for Cruz in Houston on Monday, October 22 (which is also the first day of early voting in Texas).